The invention relates to a fifth wheel coupling pin for semitrailers, for connecting the semitrailer to the fifth wheel of a tractor-trailer, having a coupling portion for locking in detent fashion into the fifth wheel, having a support portion for insertion into a receiving opening of the semitrailer that has support faces, and having a securing portion for securing the fifth wheel coupling pin against falling axially out of the receiving opening. The invention also relates to an attachment arrangement for attaching fifth wheel coupling pins to semitrailers, having a housing attached, preferably welded, to the semitrailer, which housing has a continuous, preferably conical receiving opening for receiving a support portion of the fifth wheel coupling pin, and a securing portion of the fifth wheel coupling pin protrudes out of the top of the housing oriented toward the semitrailer.
For connecting a tractor-trailer to a semitrailer, a coupling arrangement is used, comprising a coupling cradle, mounted on the tractor, with an introduction slot and securing means and with a so-called fifth wheel coupling pin or kingpin, which is secured to the semitrailer. To achieve the greatest possible compatibility between tractor-trailers and semitrailers, the dimensions of the insertion slot and of the kingpin body are standardized, for instance under DIN Standard 47080 or ISO Standard 337.
In known embodiments, the fifth wheel coupling pin comprises a standardized coupling portion, a conical support portion, and a securing portion embodied as a thread. Known attachment arrangements have a housing, which is firmly welded to the semitrailer, and a conical bore into which the fifth wheel coupling pin is inserted from below. The conical support portion of the fifth wheel coupling pin rests on the conical opening of complementary shape, so that essentially radially oriented tensile forces of the tractor or torques and essentially axially oriented forces of gravity of the semitrailer can be transmitted.
To secure the fifth wheel coupling pin against falling out axially, a castellated nut is screwed onto the thread of the securing portion that protrudes upward out of the opening into the interior of the semitrailer, and the castellated nut in turn is secured by means of a cotter pin relative to the kingpin body. During vehicle operation, fifth wheel coupling pins undergo a certain wear, so that they have to be replaced from time to time. In the known embodiment, this requires taking off the cotter pin securing means and the castellated nut, and then the worn fifth wheel coupling pin can be removed from its base and replaced. A disadvantage of the known embodiment is that castellated nut can be loosened only from the inside of the semitrailer, and additionally that the cotter pin securing means must be removed and reinstalled. Yet the cotter pin securing means cannot be omitted, because an unsecured castellated nut could come loose during vehicle operation as a consequence of slight motions of a worn fifth wheel coupling pin.